Quantification of human herpesvirus 6 in immunocompetent persons and post-mortem tissues from AIDS patients by PCR

A quantitative competitive PCR assay for human herpesvirus 6 (HHV-6) was developed, Firstly, viral burden was determined in the blood of 25 healthy persons, Using 1 pg of DNA, the prevalence of HHV-6 was 36% (9/25), Eight persons had viral loads of less than or equal to 32 HHV-6 genomes/mu g DNA, The viral burden in the ninth individual was 1.2 x 10(6) HHV-6 genome copies/mu g DNA, which remained constant over a period of 10 months, This demonstrates the persistence of a high HHV-6 load in the absence of apparent disease, Secondly, HHV-B burden was determined in 100 post-mortem tissues from seven AIDS patients and three controls, For all tissues combined, there was a statistically significant higher median viral load in AIDS patients (56 copies/mu g DNA, range 0-43 321) compared to controls (10 copies/mu g DNA, range 0-423) (P = 0.04), The precision and reproducibility of this assay will allow hypotheses concerning the pathogenic potential of HHV-B to be tested quantitatively.